In the final chariot race, Ben-hur's enemy falls from his chariot. In this scene, if you watch closely, you can see a watch on the bad guy. There was another error before they cut it. Before, you can see a plane in the sky but now they cut it.

The comment about the actor actually dying in the chariot-racing scene is incorrect. It is a very well-known and widely believed rumor. Check out this link about it: http://www.snopes2.com/movies/films/benhur.htm
And remember, even Bible teachers can be wrong! (I know, hard to believe...)

Actually, in the 1920's, a silent version of Ben-Hur was made where the actor or stunt double playing Messala did die, but, and I am assuming that this is the 1956 version with Charlton Heston, nobody died.

The stunt man was hurt but did not die, although the injuries ended his stunt career. He continued to work in the industry as a stunt coordinator after Ben-Hur, but performed no more stunts himself. His name was Yakima Canutt, and he was a former actor and a very famous stuntman. He was a good friend of John Wayne and was in some of the Duke's early films.

The man (enemy) who fell off the chariot actually died in that scene. I know that as a fact because my bible teacher told me. The people who filmed the movie asked the family of that man if they could keep that scene in the movie. So they kept it as a remembrance for the family.